Software

Software

1. High level language

   • designed to resemble a natural language such as english
   • easier to read and understand for humans
   • Examples consist of python and java
     • Is not directly executed by CPU as needs to be translated to machine code
   • Used for complex coding such as making a game for the new play station

2. Low level language

   • does not resemble natural english
   • Hard for humans to read and understand
   • Executed directly by the CPU
     • Examples consist of Little Man Computer and Machine Code
   • F1 cars use machine code / low level languages as instructions can immediately be run.

3. Stages of compilation

   • Step 1 = Lexical Analysis
     • Comments and unneeded spaces are removed, keywords are replaced by tokens
   • Step 2 = Symbol Table Construction
     • Symbol table is created which holds variables
   • Step 3 = Syntax Analysis
     • Tokens are checked to see if they match the syntax, if there is a syntax error an error message appears
   • Step 5 = Code Generation
     • Machine Code is Generated
   • Step 6 = Code Optimisation
     • Code optimisation may be employed to make it more efficient / faster
   • Step 4 = Semantic Analysis
     • Variables are checked to see if they have been declared properly and used as well as to see if they are the right data type

4. Program Construction

   • Assemblers:
     • translate assembly language to machine code, each operator and operand is replaced by its binary equivalent
   • Compilers:
     • Translate the high level code all at once to produce a machine code file
       • .exe file for example
   • Interpreters:
     • Do not create an executable file, they execute the source code by translating and executing one line at a time. Easier to find errors than compilation

5. Errors

   • Syntax Errors:
     • Occurs when text that is not valid code is found, for example print("hello) - this is missing a qoute
   • Runtime / Execution Error:
     • Occurs when the program tries to perform an impossible operation, e.g. dividing by zero
   • Logical Error:
     • When the program executes and exits with no errors however doesn't do what was expected.
   • Linking Error:
     • Occurs when a program tries to import a function from a file that does not exist
   • Rounding Error:
     • Occurs when a value is rounded and loses accuracy

6. Utility Software

   • Antivirus:
     • Routinely scans files and compares them to a database of known malware, removing or repairing infected files
   • Firewall:
     • Monitors network communication and blocks un-trusted messages
       • Defragmentation:
         • Files can become fragmented across the hard disk
   • Compression:
     • Complex algorithms are used to store data in a format that requires less space on disk without losing any content